There are many situations where it would be desirable to have a compact, relatively portable fire-fighting system readily available, particularly in forest or brush areas or in remotely located neighborhoods where full scale fire-fighting equipment is not readily available or accessible. Such a compact system should, to the extent possible, make use of the most advanced fire-fighting technology available.
The use of foam additives to water in fighting fires is well recognized as a major advance in improving the effectiveness in retarding ignition, extinguishing blazes, preventing re-ignition of burnable materials, and in indicating a coverage in both airborne drops and ground operations. Foam is particularly suited for use in forest or brush areas where it will also act as a wetting agent, exhibiting good cooling capability by blanketing burnable materials, and reducing smoke by the blanketing effect.
This system employs our previously patented foam mixing system, which is the subject of U.S. Pat. No. 5,009,244, assigned to the assignee of the present patent application, which discloses a system for mixing foam concentrate, such as a product of Ansul Wormold Corp. of Marionette, Wis., sold under the trademark ANSUL, with water in such a way that the precise desired proportion of foam concentrate is mixed with water irrespective of the quantity of water supplied to fight a fire. A significant element of this system is a differential pressure valve, the subject of U.S. Pat. No. 5,165,442, which is also assigned to the assignee of the present application. Both of the above patents are hereby incorporated by reference.
Fire fighters are concerned with the ratio of foam concentrate to water and also to the ratio of water/foam concentrate to air. If the foam concentrate provided is too low (below about 0.2%), this will result in pulsations (water slugs) in the hose. This is because there is not enough foam concentrate in the solution to form foam in the hose. A somewhat higher ratio will yield a “wetter” appearing foam. A still higher ratio will yield a “drier” appearing foam. Varying degrees of dryness or wetness are appropriate for combating different types of fires.
Because the ratio of air to water/foam solution is recognized as being very important to getting the desired type of foam output, other systems have used separate flow meters for air and for the water/foam concentrate mix. This arrangement is difficult to operate because it leaves one operator, the engineer, juggling the air and water/foam valves in an attempt to produce the desired output at the end of the hose, while the second operator, the firefighter, at the end of the hose may well be out of sight and out of earshot. So, although the second operator might recognize that the ratio was not what was needed (more or less water/foam concentrate in proportion to air), he might have difficulty conveying to the operator the need for and the kind of change needed for controlling the flow.
It is, therefore, an object of the present invention to provide a compressed air foam fire-fighting system having controls capable of setting and maintaining desired ratios of water/foam concentrate to compressed air.
It is another object of the present invention to provide a fire-fighting system incorporating the above objective, and in which the entire system is built into a framework small enough to fit in the bed of a typical full size pick-up truck.
It is a further object of the present invention to provide a fire-fighting system incorporating the above objectives and in which the ratio of foam concentrate to water is maintained irrespective of a volume of water delivered to the system.
It is a still further object of the present invention to provide a fire-fighting system incorporating the above objectives and which is capable of delivering water, water/foam concentrate, water/foam concentrate mixed with compressed air and air alone.
Other objects and advantages will become apparent from consideration of the following specification taken in connection with the accompanying drawings.